Cycles render for Facebook without color
You have to consider that materials in cycles get translated. As the  glTF 2.0 Exporter documentation says: 


  Blender supports two material settings: One for Blender Render and one for Cycles Render. Fortunately, the glTF 2.0 Materials can be simulated using the Cycles Render by implementing a custom node tree


You can't just write materials in cycles and then translate them, this will just not work. You have to use the ones provided by the repo. 

This is really well explained in the documentation (I'm assuming you're using this exporter):

https://github.com/KhronosGroup/glTF-Blender-Exporter/blob/master/docs/user.md